UNIVERSITY  OF  CALIFORNIA 
College  of  agriculture 

BERKELEY,   CALIFORNIA 


AGRICULTURAL  EXPERIMENT  STATION 
E.    J.   WlCKSON.    Director 


CIRCULAR  No.  69 


(August,  1911) 


The  Extermination  of  Morning-Glory 


By  FREDERIC  T.  BIOLETTI 


H                                                      appi 

■    ,   : 

'   .?   -.-  ,-"-••-'. ,    ,  •     •*?-.-•■.'-   , 

Fig.    1. — Vineyard   badly   infested   with   Morning-glory. 


W.    W.    SHANNON 


SACRAMENTO 

-       -       SUPERINTENDENT    OF    STATE    PRINTING 
1911 


THE  EXTERMINATION  OF  MORNING-GLORY. 

By  Frederic  T.  Bioletti. 

The  wild  morning-glory  (Convolvulus  arvensis)  is  one  of  the  most 
troublesome  weeds  in  vineyard,  orchard,  and  other  cultivated  soils.  It 
is  a  native  of  Europe,  but  is  well  distributed  throughout  California. 


Fig.  2. — Morning-glory   (Convolvulus  arvensis). 

It  grows  in  nearly  all  soils,  from  light  sand  to  heavy  clay,  and  the 
better  and  deeper  the  soil  the  more  difficult  it  is  to  eradicate.  Wherever 
it  grows  abundantly,  it  has  a  most  deleterious  effect  on  the  crops.  This 
is  particularly  true  of  any  crop  which  requires  clean  cultivation.  It 
may  completely  destroy  young  vines  and  trees,  and  will  stunt  and  render 


—  4  — 

unprofitable  old  vineyards  and  orchards.  It  is  less  harmful  to  annual 
crops  which  mature  early,  such  as  hay  or  grain,  as  it  does  not  commence 
to  grow  vigorously  until  they  are  harvested.  In  alfalfa  it  does  little  or 
no  harm,  but  remains  alive  ready  to  infest  any  susceptible  crop  which 
may  be  planted. 

In  the  worst  cases,  the  growing  of  trees  or  hoed  crops  has  sometimes 
to  be  abandoned,  and,  in  any  case  where  morning-glory  is  prevalent,  it 
necessitates  an  amount  of  extra  cultivation  variously  estimated  at  from 
$5  to  $10  per  acre. 

The  weed  is  a  perennial  with  strong,  far-reaching  roots.  The  smallest 
piece  of  root  is  capable  of  growing  and  originating  a  new  plant.  Ordi- 
nary cultivation  has  no  apparent  effect  except  to  make  it  grow  more 
vigorously.  Very  thorough  and  frequent  cultivation  with  a  good  weed- 
cutter  throughout  the  growing  season  will  keep  it  down  so  that  there  is 
no  appreciable  harm  to  the  crop.  With  vines  and  small  crops,  however, 
this  must  be  supplemented  by  a  considerable  amount  of  hand-hoeing. 

Methods  of  control.  Most  annual  and  shallow-rooted  weeds  will  die 
if  cut  off  an  inch  or  two  below  the  surface  of  the  soil.  Many  perennial 
and  deep-rooted  weeds  will  make  a  new  growth  from  the  underground 
portions.  In  most  cases  a  second  or  a  third  cutting  below  the  surface 
will  destroy  these.  A  few  will  produce  a  new  growth  even  after  repeated 
cuttings.  The  morning-glory  will  produce  a  new  growth  continuously 
every  year  even  if  cut  off  below  the  surface  every  time  it  appears  above. 

All  plant  growth  originates  in  a  bud.  When  a  weed,  therefore,  is  cut 
off  below  the  surface,  if  all  buds  are  removed  and  if  the  portions  which 
remain  in  the  ground  are  incapable  of  developing  dormant  or  adven- 
titious buds,  the  plant  dies.  Every  portion  of  the  underground  system 
of  the  morning-glory  is  capable  of  producing  adventitious  buds  with 
great  facility. 

Besides  buds,  new  growth  requires  water  and  certain  food  materials 
of  which  starch  is  typical  and  the  principal.  The  water  is  obtained 
from  the  soil  by  the  roots,  and  the  deep-root  system  of  the  mornng-glory 
keeps  it  well  supplied  in  this  respect.  The  starch  is  obtained  in  the  first 
place  by  the  leaves  from  the  air.  The  first  growth  of  a  bud,  however, 
before  mature  leaves  are  produced,  is  at  the  expense  of  a  reserve  of 
starch  laid  up  in  the  stems,  or,  where  these  are  removed,  of  that  laid  up 
in  the  roots. 

The  deeper  and  more  voluminous  the  root  system  the  greater  the 
reserve  of  food  material  available  for  new  growth.  It  is  for  this  reason 
that  the  morning-glory  is  able  to  make  a  new,  vigorous  growth  even 
after  being  cut  off  repeatedly  below  the  surface.  The  first  growth 
utilizes  the  starch  in  the  uppermost  portions  of  the  roots,  which  are 
resupplied  by  the  migration  of  starch  from  the  lower  portions.     This 


migration  is  renewed  with  each  cutting  until  the  lower  parts  of  the  root 
system  become  exhausted  of  all  available  food  material  and  die.  Finally, 
if  the  cuttings  are  sufficiently  frequent  and  continued  long  enough,  all 
remaining  reserve  starch  is  contained  in  the  uppermost  portions  of  the 
root  system,  and  one  or  two  more  attempts  at  new  growth  followed  by 
cuttings  will  exterminate  the  plant. 

This  is  not  a  new  theory,  but  the  failure  of  numerous  attempts  to 
exterminate  morning-glory  by  means  based  on  this  theory  has  thrown 
doubt  of  its  correctness  in  the  minds  of  many. 

There  are  two  causes  for  these  failures.  The  first  is  that  when  the 
morning-glory  appears  above  the  surface  it  produces  normal  green  leaves 
very  rapidly.  These  leaves  commence  the  manufacture  of  starch  imme- 
diately and  quickly  replenish  the  store  of  reserve  material  in  the  upper 
roots.  The  draft  on  the  lower  roots  is  thus  stopped,  and  they  remain 
well  nourished  and  healthy.  The  only  way  to  exhaust  the  roots,  there- 
fore, is  to  cut  off  the  new  growth  before  it  appears  above  the  surface. 
The  second  cause  is  that,  owing  to  the  voluminous  root  system  of  the 
morning-glory,  the  amount  of  reserve  starch  is  very  large.  New  growth 
will  continue  so  long  as  any  available  starch  remains,  and  it  takes  a 
large  number  of  renewals  of  growth  and  removals  of  material  by  cutting 
before  the  whole  root  system  is  exhausted. 

Roots  well  supplied  with  starch  and  capable  of  producing  new  shoots 
have  been  found  at  a  depth  of  14  feet.  In  a  rich,  deep  soil  at  Davis  a 
determination  of  the  weight  of  roots  at  different  depths  was  made  with 
the  results  shown  in  Table  I. 

TABLE  I. 
Weight  of  Morning-glory  Roots  in  Soil  at  Various  Depths. 


Weight  in  grams  to  a  cubic 

foot  July, 

1910. 

First  foot. 

; 

'    Second  foot.     |     Third  foot.          Fourth  foot. 

Fifth  foot. 

! 

j      Sixth  foot. 

Seventh  foot. 

7.2 

7.3                   7.7 

9.8 

8.4 

4.4 

1 

2.5 

Ths  indicates  that  there  is  little  difference  in  the  volume  of  roots  at 
different  levels  down  to  the  sixth  foot.  From  this  level  down  there  seems 
to  be  a  diminution.  A  micro-chemical  examination  of  the  roots  showed 
that  they  were  about  equally  well  supplied  with  starch  at  all  levels.  To 
exhaust  all  this  mass  of  food  material,  extending  to  a  depth  of  probably 
more  than  seven  feet  and  amounting  to  from  2^  to  5  tons  per  acre 
requires  a  large  number  of  cuttings  extending  over  considerable  time. 

In  order  to  determine  the  number  of  cuttings  and  the  length  of  time 
necessary,  a  test  was  made  on  ten  acres  of  bare  land  at  the  University 
Farm  at  Davis. 


6  — 


12  12a 

not 
planted 

■ 

11  11a 

]0 

B       10a- 

Fallow  in  /JJO. 

oT             oQ 

A 

\Jmeuard  planted  JJ)/0. 

14  2 

6eo6d  °^ 
o5 

3d°°     '  1 

6 


Map  of  location  of  experiments  with  Morning-glory. 

A.  "Vineyard,  untreated. 

B.  Fallow  land,  treated. 

The  numbers  indicate  the  location  of  the  holes  dug  to  obtain  the  various  samples 
of  roots. 

The  arrangement  of  the  experiment  is  shown  by  the  accompanying 
map  which  represents  20  acres.  The  eastern  half  (A),  with  the  excep- 
tion of  a  small  portion  in  the  northwest  corner,  was  planted  with  vines 
in  the  spring  of  1910.  The  western  half  (B),  was  subsoiled  to  a  depth 
of  about  13  inches  and  left  fallow.  In  the  planted  portion,  the  morning- 
glory  was  fairly  distributed  and  was  very  thick  in  a  few  areas,  notably 
]jear  the  southeastern  corner.  In  the  western  10  acres  the  morning-glory 
had  formed  a  continuous  thick  mat  over  nearly  the  whole  area,  and  was 
particularly  dense  on  the  northern  half  and  on  a  strip  along  the  southern 
border. 


Fig.  3. — Northern  half  of  plot  B,  showing  covering  of  Morning-glory.     The 
dark  shaded  portions  indicate  the  area  covered  with  Morning-glory. 


The  vineyard  portion  was  given  ordinary  good  cultivation  with  weed- 
cutters  and  hoes.  The  same  treatment  was  given  to  the  western  10  acres 
up  to  June  13th.  During  the  growing  period  before  June  13th  the 
morning-glory  grew  vigorously,  and  twice  appeared  above  the  surface 
in  sufficient  quantity  to  render  the  whole  piece  green.  From  June  13th 
until  June  27th  the  whole  western  10  acres  was  gone  over  with  a  weed- 
cutter  every  seven  days.  It  was  found  that  a  considerable  amount  of 
growth  became  visible  at  the  end  of  seven  days,  and  from  June  27th  to 
September  13th  the  weed-cutter  was  passed  over  the  whole  piece  every 
five  days.  After  June  27th,  therefore,  no  morning-glory  appeared  above 
the  surface. 

At  the  end  of  the  growing  season,  in  order  to  estimate  the  effect  on 
the  roots  of  various  modes  of  treatment,  weighings  were  made  of  the 
amount  of  roots  in  each  cubic  foot  of  soil  to  a  depth  of  3  or  4  feet  in 
various  parts  of  the  field. 

In  uncultivated  soil,  where  there  was  a  heavy  growth  of  morning- 
glory,  outside  the  20  acres,  an  average  of  15.8  grams  of  roots  was  found 
in  a  cubic  foot  of  soil  as  shown  in  Table  II. 


TABLE  II. 
Weight  of  Morning-glory  Roots  in  Uncultivated  Soil. 
Weight  in  grams  per  cubic  foot  November  14,  1910. 


First  foot. 

Second  foot. 

Third  foot. 

Fourth  foot. 

1                  '! 

Total. 

J     Mean. 

Sample  13 

Sample  15  

Sample  16  

15.0 
12.6 
26.0 

7.5 
23.3 
12.4 

7.5 

24.2 
14.2 

30.0 
85.3 
64.0 

1 

10.00 

25.2 
11.4 

21.3 
16.0 

Average  weight  of  roots  in  1  cubic  foot  of  soil  equals  15.8  grams. 

On  the  same  date  weighings  were  made  of  the  amount  of  roots  in  a 
cubic  foot  of  soil  in  the  southeastern  corner  of  the  vineyard,  10  acres, 
where  ordinary  good  cultivation  had  been  practiced.  The  results  differ 
little  from  those  in  uncultivated  soil,  the  average  being  15.1  grams  in 
1  cubic  foot  as  shown  below : 


TABLE   III. 

Weight  of  Morning-glory  Roots  in  Well  Cultivated  Soil. 

Weight  in  grams  per  cubic  foot  November  14,  1910. 


First  foot. 

Second  foot. 

Third  foot. 

Total. 

Mean. 

Sample 

1  

9.4 

17.4 

16.4 

43.3 

14.4 

Sample 

2  

6.7 

14.7 

24.5 

45.9 

15.3 

Sample 

3  

20.0 

29.0 

20.5 

69.5 

23.2 

Sample 

14  

7.2 

7.3 

7.7 

22.2 

7.5 

Average  weight  of  roots  in  1  cubic  foot  of  soil  equals   15.1   grams. 


The  result  of  ordinary  good  cultivation,  therefore,  on  the  roots  in  the 
upper  three  feet  of  soil  is  apparently  nil.  The  injury  due  to  repeated 
cutting  off  of  new  growth  is  probably  counteracted  by  the  better  condi- 
tions of  growth  due  to  cultivation.  Micro-chemical  examination  of  the 
roots  showed  that  in  all  cases  they  were  well  supplied  with  starch. 

Weighings  were  also  made  of  the  amount  of  roots  in  a  cubic  foot  of 
soil  in  various  parts  of  the  10  acres  where  weed  cutting  every  five  days 
had  been  practiced,  with  results  shown  in  the  following  table : 


TABLE  IV. 

Weight  of  Morning-glory  Boots  in  Soil  Weed-cut  Every  Five  Days. 

Weight  in  grams  per  cubic  foot  November  14,  1910. 


Second  foot. 


Third  foot. 


Sample  4 
Sample  5 
Sample  6 
Sample  7 
Sample  8 
Sample  9 
Sample  10 
Sample  11 
Sample  12 


5.0 
5.7 

.7 
1.5 
2.5 
5.5 
5.5 
14.0 
18.0 


4.6 
3.5 

.2 
3.4 
1.9 

2.5 
9.0 
8.5 
5.0 


5.2 
4.5 
.2 
1.0 
1.0 
3.0 
5.0 
6.5 
4.0 


14.8 

13.7 

1.1 

5.9 

5.4 

11.0 

19.5 

29.0 

27.0 


4.9 
4.6 
.4 
2.0 
1.8 
3.7 
6.5 
9.7 
9.0 


Average  weight  in  1  cubic  foot  of  soil  equals  4.7  grams. 

The  result  of  the  continuous  weed  cutting  is  shown  here  by  a  diminu- 
tion of  about  70  per  cent  in  the  average  weight  of  roots  in  a  cubic  foot 
of  soil.  Samples  5,  6,  and  7  were  taken  from  a  part  of  the  field  where 
the  morning-glory  had  been  less  dense  than  in  the  major  portion.  If 
we  omit  these  weighings,  the  average  would  be  6.4  grams  in  a  cubic  foot, 
which  indicate  a  diminution  of  weight  of  over  60  per  cent. 

If  this  decrease  in  the  quantity  of  roots  were  the  whole  effect  of  the 
work  it  would  not  be  worth  the  expense.  Micro-chemical  examination 
of  the  roots,  however,  showed  that  many  of  them  were  almost  devoid  of 
starch  and  that,  in  all,  the  amount  of  starch  was  very  small  compared 
with  that  of  roots  from  the  other  sources.  This  is  clearly  shown  by  the 
photo-micrographs  on  following  page. 

This  almost  complete  absence  of  starch  indicates  an  exhaustion  of 
the  reserve  store  of  food  material.  It  is  by  means  of  this  reserve  that 
plants  commence  their  growth  in  the  spring  after  remaining  dormant 
during  the  winter.  The  first  spring  growth  is  more  or  less  vigorous  in 
proportion  to  the  amount  of  reserve  food.  If  this  reserve  is  lacking  or 
too  small  there  will  be  no  growth  at  all. 

That  the  continuous  weed  cutting  had  sufficiently  exhausted  the 
reserve  food  materials  of  the  roots  was  shown  the  following  year.  By 
the  middle  of  June,  1911,  the  morning-glory  in  uncultivated  soil  was 
in  bloom  and  growing  vigorously.  In  block  A,  in  spite  of  vigorous  use 
of  cultivator  and  hoe,  it  was  growing  strongly  in  many  places.     In 


wiwfZjKF^/Kbr*' ^'^t^ 

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lb     '        •*    *       '■*"■                         / 

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Fig.  4. — A.  Section  of  Morning-glory  root  from  uncultivated  soil.  B.  Section  of 
Morning-glory  root  from  soil  where  weed-cutter  was  used  every  five  days.  (Enlarged 
about  25  diameter.) 

Note. — Dark  contents  of  cells  in  bark  of  A  indicating  abundance  of  starch  and 
white  contents  of  cells  in  bark  B  indicating  complete  absence  of  starch.  (Stained  with 
Iodine  solution.) 


—  10  — 

block  B  a  careful  search  of  the  whole  10  acres  revealed  less  than  half  a 
dozen  shoots  of  morning-glory. 

"Weighings  were  then  made  of  all  the  roots  which  could  be  found  in 
the  first  four  feet  in  locations  corresponding  to  those  where  similar 
determinations  had  been  made  in  November,  1910.  The  following  table 
gives  the  results: 


TABLE  V. 

Weight  of  Morning-glory  Roots  in  Treated  and   Untreated  Soil. 

Weight  in  grams  per  cubic  foot  June  17,   1911. 


!                     i                    | 

Firstfoot.         Second  foot.        Third  foot. 

i 

Fourth  foot. 

Total.         j      Mean. 

Untreated- 
Sample  13a 

Sample    3a 

Treated — 
Sample    6a 

11.5 
9.3 

.4 

13.0 
21.0 

.2 

10.7 
17.2 

.2 

1.5 

.6 

5.9 
9.1 

41.1 
56.6 

.8 

2.5 

9 

10.2 
14.2 

.2 

Sample  10a 

.1 

.8 

Sample  11a 

.1 

.2 

.2 

Sample  12a 

:.. 

1 

i 

Sample  13a  was  taken  from  uncultivated  ground  near  to  where 
sample  13  had  been  taken  in  November,  1910.  The  roots  were  large  and 
healthy. 

Sample  3a  was  taken  from  nearth  the  southeast  corner  of  the  vineyard 
close  to  where  sample  3  had  been  taken  in  November,  1910.  The  roots 
were  larger  and  apparently  more  vigorous  than  those  of  sample  13a. 

Samples  6a,  10a,  11a,  and  12a  were  taken  from  block  B  near  to  where 
the  corresponding  samples  had  been  taken  the  previous  November.  The 
weight  was  insignificant  in  all  cases  and  with  the  exception  of  sample  10a 
the  roots  were  all  dead  and  decayed.  Even  in  sample  10a  no  live  roots 
were  found  in  the  upper  foot.  The  few  living  roots  found  in  the  third 
foot  were  devoid  of  starch,  and  therefore  incapable  of  growing. 

Towards  the  end  of  July  some  morning-glory  shoots  began  to  appear 
in  several  areas  of  the  10  acres.  These  areas  were  in  spots  where  the 
plow  had  turned  in  the  preliminary  deep  plowing  of  the  piece.  The 
ground  was  left  harder  in  these  spots  and  the  surface  rougher,  so  it  is 
probable  that  the  weed-cutter  had  not  worked  so  perfectly  there.  Over 
most  of  the  10  acres,  however,  the  weed  had  been  completely  extirpated. 

The  10  acres  were  gone  over  carefully  and  every  shoot  of  morning- 
glory  counted  and  the  numbers  compared  with  the  number  of  shoots 
growing  in  an  untreated  area.  The  result  showed  that  the  weed  had 
been  reduced  99.95  per  cent — that  is,  there  was  only  one  plant  left  for 
every  2,000  present  before  treatment. 

This  experiment  may  be  taken  as  a  complete  demonstration  of  the 
possibility   of   the   practical   extermination   of   morning-glory   in    one 


—  11  — 

season  by  weed  cutting  repeated  with  sufficient  frequency,  where  the 
character  of  the  soil  and  the  condition  of  the  surface  are  favorable  to 
thorough  work. 

The  main  points  to  be  observed  are : 

1.  The  weed-cutter  must  be  of  such  a  form  that  no  part  of  the  ground 
is  missed.  The  form  used  was  a  straight  knife  4  inches  wide  and  4  feet 
6  inches  long.  (See  figure  5.)  This  was  attached  to  a  riding  cultivator 
drawn  by  two  horses.  It  was  attached  perpendicularly  to  the  direction 
taken  by  the  cultivator.  By  overlapping  about  6  inches  on  each  passage 
through  the  piece,  it  was  easy,  with  steady  horses,  to  avoid  missing  any 


Fig. 


-Weed-cutter  used  in  the  experiments. 


spot.    On  rough  land  this  would  be  more  difficult ;  where  vines,  trees,  or 
other  crops  are  growing,  impossible. 

2.  Every  weed  cutting  should  take  place  before  any  shoots  appear 
above  the  surface.  The  smallest  growth  of  green  leaves  commences  to 
renew  the  starch,  and  therefore  diminishes  the  exhaustion  of  the  starch 
supply  of  the  roots,  which  is  the  object  of  the  cutting.  Any  consider- 
able growth  of  leaves  replenishes  the  starch  supply  completely,  as 
illustrated  by  the  effect  of  the  ordinary  cultivation  of  block  A. 

3.  The  weed  cutting  should  continue  until  the  coolness  of  late  autumn 
prevents  the  growth  of  the  weed.  A  growth  in  autumn  would  probably 
furnish  the  partially  exhausted  roots  with  sufficient  food  materials  to 


—  12  — 

preserve  them  during  the  winter  and  to  promote  a  new  growth  the  fol- 
lowing spring.  How  early  in  the  season  it  is  necessary  to  commence 
thorough  weed  cutting  was  not  determined  by  the  experiment.  June  1st, 
at  Davis,  after  the  morning-glory  had  already  made  a  vigorous  growth, 
is  evidently  not  too  late. 

4.  The  depth  at  which  the  weed  knife  should  be  run  for  the  most 
economical  work  is  another  point  which  was  not  determined.  In  the 
experiment,  the  depth  did  not  average  more  than  3  inches.  By  running 
the  knife  deeper — say  5  to  6  inches,  it  is  probable  that  the  time  between 
cuttings  could  be  lengthened  and  the  number  of  cuttings  diminished 
without  any  inferiority  in  the  results. 

The  cost  is  easily  estimated  from  the  above  data.  From  June  1st 
to  November  1st  is  153  days,  which  represents  30  weed  cuttings.  The 
10  acres  treated  required  2  horses  and  1  man  one  day  for  each  weed 
cutting,  so  that  the  total  work  required  30  days,  which,  at  $3.00  per  day 
for  man  and  team,  represents  $90.00,  or  $9.00  per  acre. 

"Wherever  the  morning-glory  can  be  exterminated  in  a  piece  of  land 
for  a  cost  not  exceeding  $10.00  per  acre,  it  is  undoubtedly  economical, 
and  it  would,  in  all  such  cases,  pay  to  delay  the  planting  of  a  vineyard 
or  orchard  in  infested  land  a  year  for  this  purpose.  The  cost  is  little 
more  than  has  to  be  expended  every  year  in  an  infested  vineyard  merely 
to  keep  the  morning-glory  down  sufficiently  to  prevent  injury  to  the 
vines  and  without  hope  of  extermination. 

Other  methods  of  treatment  have  been  suggested,  but  all  which  give 
promise  of  successful  results  depend  on  the  same  principle :  The  promo- 
tion of  continuous  new  growth  to  exhaust  the  reserve  matter  of  the  root 
system  and  the  removal  of  this  growth  before  it  has  an  opportunity  to 
replenish  these  food  reserves. 

Penning  chickens  or  hogs  on  an  infested  spot  has  been  recommended, 
but  it  is  doubtful  if  this  would  be  successful  unless  a  comparatively 
large  number  of  animals  were  kept  continuously  on  a  small  patch. 
Covering  the  ground  with  black  building  paper  has  also  been  suggested, 
and  would  undoubtedly  be  effective  if  the  growth  of  the  plants  could  be 
prevented  from  reaching  the  light  between  the  sheets  of  paper.  In  the 
presence  of  heavy  winds  this  would  be  difficult,  and  in  any  case  probably 
more  expensive  than  efficient  weed  cutting. 


